Many people who suffer from a chronic disease require regular medication to ensure adequate control of the disease. For example, asthmatics normally require a daily dose of an anti-inflammatory drug to prevent an asthma attack. In addition, asthmatics often require a different dose and/or a different anti-inflammatory drug to treat an asthma attack. In each case, the amount of drug required by the patient will depend on the severity of the asthmatic condition or the severity of asthma attack. At present, a patient is supplied with an inhaler device which dispenses a pre-determined quantity of medication, and which does not take into account the precise present day condition of the patient. WO95/22365 discloses an inhaler that measures a specific feature of the disease, for example the inhalation airflow, and processes this information to advise the patient, inter alia, on changes in timings or dosages of drug to be taken. It is however, up to the patient to implement these changes. Furthermore, any changes in drug dosage will be based on the patient's condition at the time the previous dose was administered and not the current condition of the patient.